Lactose maldigestion (i.e., lactase non‐persistence, lactase restriction) is a very common condition worldwide. It is more common in Asian and African populations than in Caucasians, but its prevalence in America and in some European populations is also fairly high. The causes of both primary and secondary lactose maldigestion have been well established since its discovery in the 1960s. Until now, research has focused on lactose maldigestion, but symptoms have received relatively little attention. Because the presence or absence of symptoms and their severity guide the food choices of an individual and his/her need to consult health professionals, knowledge of the symptoms of lactose intolerance should be of concern to the health authorities and to the food industry. Despite the vast amount of research carried out on lactose intolerance, many questions still remain open. In this review, both recent works and early literature on lactose intolerance with regard to milk composition, gastric emptying, and functional bowel disorders are presented.